layerdblend.hlsl

@(at-point 'surface-struct
  '(
    (float3 albedo1 ;)
    (float3 albedo2 ;)
    (float blend ;)))

@(at-point 'surface-calc
  '(
    (surface . albedo1 = ... ;)
    (surface . albedo2 = ... ;)
    (surface . blend = ... ;)))

@(at-point 'surface-params """
  params.albedo = lerp(surface.albedo1, surface.albedo2, surface.blend);
""")

@(include "surface.frag")

multiblend.hlsl

@(log "Building %d layer blend" numLayers)

@(at-point 'surface-struct
  (map 
     (lambda (i) '(
       (float3 ,(concatenate "albedo" i) ;)
       (float ,(concatenate "blend" i) ;))
     (range 0 numLayers)))

@(at-point 'surface-calc
  '(...))

@(at-point 'surface-params 
  (map
    (lambda (i)
      (list "params.albedo = lerp(params.albedo, surface." (concatenate "albedo" i) ", surface." (concatenate "blend" i) ");"))
      (range 0 numLayers))) 

@(include "surface.frag")

surface.hlsl

struct LightParams {
  float3 albedo;
};

struct Surface {
  @(point 'surface-struct)
};

void main()
{
  Surface surface;
  @(point 'surface-calc)
  ...
  LightParams params;
  params.albedo = float3(0,0,0);
  @(point 'surface-params)
  float3 color = evalLights(params);
  @(point 'modify-color)
  out_color = color;
}